In a one-year league you do what it takes to win. I like the Benn for Letang deal (but beware he may get rested before playoffs). The other two I like as well, but I think you're giving up the name value, so if you can make it a 2 for 2 where you get the better player in the second half of the deal too, that's how you really make out like a bandit in getting ready for playoffs.
Pietranelo only plays 3 times each of the first two weeks and hasn't done much all year. I would try shopping him around for a guy like Doughty, Weber, or even a guy like Petry.